(sinα-cosα)/(sinα+cosα)=1/3sinα=2cosα (cosα)^2=1/5cos(π/3+α)的四次方-cos(π/6-α)的四次方=[cos(π/3+α)]^4-[sin(π/3+α)]^4={[cos(π/3+α)]^2-[sin(π/3+α)]^2}*{[cos(π/3+α)]^2+[sin(π/3+α)...